High-frequency RIFD printer

ABSTRACT

There is disclosed a printer having a print head and a high frequency magnetic coupler to magnetically couple with high frequency RFID transponders in a web at or near the print head. The coupler couples magnetically to only one transponder at a time that is generally aligned with one or more inductors, and magnetic radiation from the inductor(s) may be at least partly shielded from upstream transponders, and a grounded conductor in the upstream side of the coupler diminishes radiation to upstream transponders. One embodiment includes spaced inductors disposed along a generally transverse line across the web, and in another embodiment an elongate inductor extends along a line generally transverse of the web.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application of Lance D.Neuhard, Ser. No. 11/726,259, filed Mar. 21, 2007. Lance D. Neuhard isalso named an inventor in U.S. patent application Ser. No. 10/873,979,filed Jun. 22, 2004.

BACKGROUND

1. Field

The field is RFID printers.

2. Brief Description of the Prior Art

The following prior art is made of record: U.S. Pat. No. 3,243,521; U.S.Pat. No. 3,335,412, U.S. Pat. No. 3,566,045; U.S. Pat. No. 5,833,377;U.S. Pat. No. 3,936,834; U.S. Pat. No. 3,965,474; U.S. Pat. No.3,987,448; U.S. Pat. No. 4,312,003; U.S. Pat. No. 4,805,232; U.S. Pat.No. 5,014,071; U.S. Pat. No. 6,848,616; U.S. Pat. No. 7,154,447; U.S.Pat. No. 7,209,090; Publication No. US 2005/0280537; Pub. No. US2007/0013520; Coilcraft, Inc. SMT Power Inductors—DS5022 P Series,Document 188-1 Copyright 2006; Johnson Components MMCX Straight PC MountJack Receptacle, 4 pages; and Texas Instruments Tag-it HF-I TransponderInlays Reference Guide 11-09-21-053 May 2002.

SUMMARY

An embodiment of the invention includes a printer with a print head, aweb path for a longitudinally extending web of record members havinglongitudinally spaced high frequency RFID transponders, the web pathextending in a downstream direction to the print head, and a highfrequency magnetic coupler disposed along the web path, the couplerbeing capable of magnetically coupling with the transponders by writingto and/or reading the transponders one-at-a-time, the coupler includingat least one inductor capable of radiating or receiving magnetic energy,each inductor having a magnetizable core and an energizable windingsurrounding the core, and the coupler being disposed to radiate orreceive magnetic energy at a level to write to or read a transponder inthe web generally aligned with the core but insufficient to write to orread any transponder in the web not generally aligned with at least onecore. It is preferred that at least one grounded conductor be positionedupstream of the core(s) to diminish magnetic radiation to transpondersupstream of the conductor(s). It is also preferred to provide aplurality of inductors disposed generally transversely across the webpath. When a plurality of inductors are used, they are preferablyconnected in series and mounted on a circuit board and the windings ofthe inductors are wound in the same direction. The coupler is preferablypositioned near the print head such as between a guide member and theprint head, however, the coupler can be positioned on the print head oron the substrate for the print head.

Another embodiment includes a printer having a print head, a web pathfor a longitudinally extending web of record members havinglongitudinally spaced high frequency RFID transponders, the web pathextending in a downstream direction to the print head, and a highfrequency magnetic coupler disposed along the web path, the couplerbeing capable of magnetically coupling with the transponders by writingto and/or reading the transponders one-at-a-time, the coupler includingan inductor capable of radiating or receiving magnetic energy, theinductor having a single magnetizable core and an energizable windingcoupled to the core, and the coupler being disposed to radiate orreceive magnetic energy at a level to write to or read a transponder inthe web generally aligned with the inductor but insufficient to write toor read any transponder in the web not generally aligned with theinductor, wherein the core and the winding are elongate and extendgenerally transversely across the web path to provide a substantiallyuniform magnetic field across the web. The coupler preferably includes agrounded conductor to help prevent magnetic energy from affectingtransponders located upstream and downstream of the inductor.

BRIEF DESCRIPTION OF THE DIAGRAMMATIC DRAWINGS

FIG. 1 is a side elevational view of an embodiment of a printer;

FIG. 2 is a top plan view of a fragmentary portion of the printer asviewed perpendicular to the web path illustrated in FIGS. 1 and 4;

FIG. 3 is a top plan view showing the magnetic coupler in relation to anarrow web of high frequency RFID transponders;

FIG. 4 is a side elevational view of the magnetic coupler mounted to theprinter in relation to a web of RFID transponders;

FIG. 5 is a top plan view of a printed circuit board showing variousconnections;

FIG. 6 is a bottom plan view of the circuit board shown in FIG. 5;

FIG. 6A is a fragmentary bottom plan view showing a portion of theprinted circuit board;

FIG. 7 is a top plan view similar to FIG. 3 showing the RFID transponderoffset from the centerline of the web of record members;

FIG. 8 is a pictorial view of an inductor used in the magnetic coupler;

FIG. 9 is a fragmentary view of magnetizable parts and a winding of aninductor;

FIG. 10 is a pictorial view of a connector used on the circuit board;

FIG. 11 is a fragmentary sectional view of the circuit board and theconnector;

FIG. 12 is a circuit diagram of a high frequency RFID reader/writer anda magnetic coupler with multiple inductors;

FIG. 13 is a circuit diagram of a magnetic coupler with a singleinductor;

FIG. 14 is a side elevation view similar to FIG. 4 of an alternativemagnetic coupler mounted to the printer in relation to a web of highfrequency RFID transponders;

FIG. 15 is a top plan view of the alternative magnetic couplers inrelation to a web of transponders;

FIG. 16 is an elevational view of the magnetic coupler of FIG. 15 asviewed from the upstream side;

FIG. 17 is a view similar to FIG. 16, but showing a conductor wallbroken away for clarity;

FIG. 18 is a bottom plan view of the magnetic coupler; and

FIG. 19 is an alternative circuit diagram of a high frequencyreader/writer and the magnetic coupler also shown in FIGS. 14 through18.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference initially to FIG. 1, there is shown a printer generallyindicated at 40 which is the same in many respects to the printer 40disclosed in U.S. Pat. No. 5,833,377 and the printer 40 disclosed inpatent application U.S. Publication No. US2005/0280537, the disclosuresof both of which are incorporated by reference in their entireties. Theprinter 40 of the present application differs in certain respects fromthe printers of U.S. Pat. No. 5,833,377 and Publication No. US2005/0280537 as will be apparent from the description and drawings ofthe present application. For example, the printer disclosed in U.S. Pat.No. 5,833,377 is not disclosed as having RFID reading and/or writingcapabilities, while the printer disclosed in U.S. Publication No.2005/0280537 has electromagnetic ultra high frequency (UHF) RFID readingand/or writing capabilities.

While the embodiment of the present application is illustrated inconnection with a thermal printer using dot heating elements to createimages such as bar codes, graphics, alphanumeric characters and thelike, it is also useful with printers such as ink jet, laser,xerographic, impact and other types of printers.

The printer 40 of the present application can have a generally vertical,electrically conductive, metal frame plate 71 and an electricallyconductive metal base plate 120. A movable mounting member 56 ispivotally mounted to the frame plate 71 about hinge blocks 73 (only oneof which is shown). A roll R can be mounted on a suitable mountingmember as shown for example in U.S. Pat. No. 5,833,377 and PublicationNo. US2005/02805037. The roll R can comprise a web C of record membersRM. The record members RM are illustrated to comprise the web C whichcan include a carrier web W coated with a release coating R′ to which aseries of pressure sensitive labels L can be releasably adhered by tackyor pressure sensitive adhesive A (FIG. 2). If desired, the web C ofrecord members RM can be comprised of a web of RFID tags or RFID forms.The web C is shown to be paid out of the roll R and can pass beneath aguide roller 62′ rotatably mounted by a bracket 62″ to beneath a guidemember 60 which is part of a web guide generally indicated at 62. Anysuitable web guide, for example, just a member or members with one ormore guide surfaces or a roller or rollers can be used instead, ifdesired. The nature of the web guiding is not critical. The web C passesdownstream from a high frequency (HF) magnetic coupler 20 toward a printhead 69 along a web path WP. The positioning of the roll R and theroller 62′ do not affect the web path WP, however, the guide member 60assures that the taut web C remains optimally located with respect tothe coupler 20. The web path WP extends between the guide member 60 orany other suitable guide and the print head 69. The coupler 20 ispreferably near or close to the print head 69. The coupler can insteadbe on the print head 64 or on the substrate for the print head 69. Theweb C is illustrated to pass between the print head 69 and platen roll63. A delaminator 64′ in the form of a peel bar 64′ is provideddownstream of the guide member 60 and preferably adjacent the nipbetween the print head 69 and the platen roll 63. However, thedelaminator 64′ can alternatively comprise a peel roller (not shown). Alabel L can be delaminated at the delaminator 64′ where the carrier webW makes an abrupt change in direction and is advanced downwardly by amotor 165 between a motor-driven roll 65 and a spring-urged back-up roll66. A spring 66′ is used to urge the back-up roll 66 toward the roll 65so that the web W is pressed between the rolls 65 and 66. From there thecarrier web W passes about an accurate guide plate 170 and through anexit opening 49.

The illustrated printer 40 can use an ink ribbon IR wound into a supplyroll SR. The ink ribbon IR can be paid out of the supply roll SR and canpass beneath a ribbon guide 57 to the nip between the print head 69 andthe platen roll 63 and from there the ink ribbon IR can pass partiallyabout a guide 58 and onto a driven take-up roll TR.

The magnetic coupler 20 is shown to be mounted on an electricallyconductive shield 501. The shield 501 also mounts the delaminator 64′which is better shown for example in Pub. No. US 2005/0280537. Theshield 501 includes a vertical portion 504 and an inclined portion 503which mounts the coupler 20. The shield 501 is electrically grounded tothe base plate 120 which is in turn electrically grounded.

With reference to FIG. 2, there is shown the web C illustrated toinclude the carrier web W to which labels L are releasably adhered bythe adhesive A. The label L can contain high frequency (HF) magneticRFID transponders T not shown in FIG. 2 for clarity but diagrammaticallyillustrated in FIGS. 3, 4 and 7. The web C is broken away in FIG. 2 toshow an embodiment of the coupler 20 which underlies the web C. FIG. 2shows the inductors L1, L 2, L 3, L 4 and L5 mounted on a printedcircuit board 21, without showing various conductive traces of thecircuit board 21 for clarity. Such conductive traces are, however, shownin FIGS. 5, 6, 6A and 11. A transversely extending centerline CL1 of oneof the labels L is shown. The centerline CL1 is illustrated to be midwaybetween leading and trailing edges LE and TE of the labels L. Alongitudinally extending centerline CL2 of the web C is also shown. Thecenterline CL2 extends midway between side edges S1 and S2 of the labelsL. The centerlines CL1 and CL2 of the labels L are also the centerlinesof the high frequency magnetic transponder T in the embodiment shown inFIG. 2.

FIG. 3 is a view similar to FIG. 2 but showing two labels L in fulllines and the intervening label L in phantom lines PL1 and the carrierweb W in phantom lines PL2 for clarity. The transponder T is illustratedby solid lines in the centrally located label L which overlies thecoupler 20. The web C passes from right to left in the downstreamdirection of the arrow AR in FIGS. 2 through 4 toward the print head 69.As shown in the drawings, the magnetic coupler 20 is positioned upstreamof the print head 69 along with web path WP and, stated differently, theprint head 69 is downstream of the coupler 20 along the web path WP.

In FIG. 3, the transponder T is shown to have an RFID chip or inlay 22connected to the ends of winding 23. The transponder T is shown to becentered transversely with respect to the label L, and the label L andthe transponder T are shown centered transversely with respect to thecoupler 20. The inductors L1 through L5 are shown in FIG. 3 to becentered on the circuit board 21 both transversely and longitudinally ofthe web C. The centerline CL1 is shown to pass through the centers ofthe inductors L1 through L5 and the centerline CL2 passes through thecenter of the inductor L3. In FIG. 3 the web C is shown to be narrowerthan in FIG. 2 so only three indicators L2, L3 and L4 are within theinner periphery I of the transponder T.

FIG. 4 is an enlarged elevational view taken along line 4-4 of FIG. 3,but showing the web C in section for clarity. The transponder T is shownto have many more turns in FIG. 4 than in FIG. 3. A lesser number ofturns of the winding 23 is shown in FIG. 3 for clarity to avoidexcessive crossing of lines. In FIG. 4 the inductors L1 through L5 areshown to be aligned with a gap G within the inner periphery I of thewinding 23. However, it is preferred that the writing to or reading ofthe transponder T be done at the leading or trailing portions LP or TPof the winding 23 where the centerline CL1 is aligned with the leadingportion LP or the trailing portion TP. However, the writing to orreading can be done at the center of the gap G, but this is not the mostpreferred location. One or more of the inductors L1 through L5 isparticularly effective in writing to and/or reading data from thetransponders T one-at-a-time. When energized by a signal, the coupler 20causes a magnetic field to extend along the centerline CL3 as viewed inFIG. 4 in a torodial pattern to cause the transponder T which is alignedwith the coupler 20 to be written to. Conversely, the transponder Tretransmits magnetic energy along the centerline CL3 to cause one ormore of the inductors L1 through L5 to read the data from thetransponders. The web C can either be stationary or moving when thewriting to or reading occurs.

FIG. 4 shows the circuit board 21 secured to the inclined portion 503 bya stand-off generally indicated at 24. The stand-off 24 may comprise apair of electrically conductive hex-shaped rods 25 secured byelectrically conductive screws 26 to the circuit board 21 and to theinclined portion 503.

With reference to FIG. 5, there is shown the top of the circuit boardprinted with conductive traces 27 through 33. The inductors L1 throughL5 are shown in phantom lines as they would appear over electricallyconductive traces 27 through 33. Specifically, the inductor L1 isconnected to enlargement 28′ on the trace 28 and to enlargement 29′ ofthe trace 29; the inductor L2 is connected to enlargement 29″ of theconductive trace 29 and to enlargement 30′ of the trace 30; the inductorL3 is connected to enlargement 30″ of the trace 30 and to enlargement31′ of the trace 31′; the inductor L4 is connected to enlargement 32′ ofthe trace 32 and to enlargement 32″ of the trace 32; and inductor L5 isconnected to enlargement 32″ and to the trace 33. The traces 27, 28 and33 are connected to respective plated-through holes 34, 35 and 36. Theplated through-hole 35 is electrically connected to an electricallyconductive trace 41 (FIG. 6A) at the plated through-hole 35. Two of thefour screws 26 extend through the holes 34 and 36 and clamp againstconductive areas 27 and 33, so that the conductive areas 27 and 36, thescrews 26 of the standoff 24, the shield 501 and the base plate 120 areall electronically connected and grounded.

It is preferred that the inductors L1 through L5 be arranged with theirstart ends ST and finish ends F in alignment so that the start end ofone inductor be connected to the finish end F of the adjacent inductor.For example, the start end ST of the inductor L1 is connected to thefinish end F of the inductor L2, and the start end 57 of the inductor L2is connected to the finish end F of the inductor L3, and so on. Thefinish ends F are most preferably aligned with the conductor 38 and onopposite sides of the printed circuit board 21, as shown.

FIG. 6 shows the bottom or underside of the printed circuit board 21 andconnected electrically conductive areas 37 and 39 and a conductor 38integral with the conductive areas 37 and 39. While the conductor 38 isshown to be an electrically conductive trace as are the areas 37 and 39,the conductor 38 can be a wire, or wires, or one or more webs orstripes. The trace 38 may be relatively wide and is disposed at least atthe upstream side of the inductors L1 through L5. A zone 37′ bounded bya phantom line within the trace 37 is shown to have components R1, C1,C2, C3 and a connector CN1 mounted in it. These components are alsoshown in FIG. 12. The zone 37′ contains both conductive andnon-conductive areas which enable connections of these components toeach other and in turn to the inductor L1. FIG. 6A shows the connectionsin the zone 37′. Stippling to show conductive portions within the zone37′ has been omitted in FIG. 6 for clarity.

FIG. 6A shows the construction of the underside of the circuit board 21at the conductive area 37. Portions of the area or trace 37 are strippedaway at gaps A′ to form electrically conductive traces 39, 40 and 41.The signal enters the trace 39 at pin 88 at portion 42. The resistor R1is connected to portions 43 and 44. The capacitor C1 is connected toconductive portion 40 and to the conductive area portion 40′ of theconductive area 37 (which is at ground). The capacitor C2 is connectedto conductive portions 45 and 46. The capacitor C3 is connected toconductive portions 47 and 48. The portions 42 and 43 are part of thetrace 39, the portions 44, 45 and 47 are part of the trace 40, and theportions 46 and 48 are part of the trace 41. All the traces 39, 40 and41 are electrically isolated from the conductive area 37 by anon-conductive gaps or non-conductive areas A′.

With reference to FIG. 7, there is shown a web C1 with a carrier web W,with each label L containing a high frequency (HF) magnetic transponderT′. It is to be noted that the transponder T′ is offset from thecenterline CL2 and is elongate in the direction of the web path WP. Inparticular, the longitudinal dimension of the transponder T′ is greaterthan its transverse dimension with respect to the web C. In otherrespects the transponder T′ is similar to the transponder T in that ithas a winding 23′ connected at its end to an RFID chip 22′. In that thetransponder T′ is offset, it is only the inductor L2 that is alignedwith the transponder T′. Nevertheless, the inductor L2 writes to orreads the transponder T′ even though magnetic coupling is weaker betweenthe transponders T′ and the inductors L1 and L3 through L5.

With reference to FIGS. 8 and 9, there is shown an inductor, for exampleL1, having a core 75. The inductors L1 through L5 are preferablyidentical. The core 75 is shown to have a central core portion 76integrally molded with end plates 77 and 78. A winding 79 is wrappedabout the core portion 76 between the end plates 77 and 78. In theillustrated embodiment the winding 79 makes three and a half (3½) turnsand is connected at its opposite ends to electrically conductiveconnectors 80 and 81. The end plate 78 and a magnetic field limiter orshield 82 can be adhesively or otherwise suitably secured to a base 83(not shown in FIG. 9). The shield 82 and end plates 77 and 78 are shownto be circular cylindrical. The core 75 and the shield 82 can becomposed of a suitable magnetizable material such as ferrite. It isnoted that the core 75 and in particular end plates 77 and 78 as well asthe winding 79 are spaced from the shield 82 to provide an air gap. Theshield 82 limits the magnetic radiation from and to the core 75 so thattransponders T or T′ upstream and downstream are not written to or read.The shield 82 does not shield, interfere with or limit magneticradiation between the cores 75 and the transponder T (or T′) beingwritten to or read. Rather, the shield 82 allows the magnetic radiationfrom the cores 75 to pass to and from the transponder T (or T′) which isin alignment with the cores 75.

The inductors L1 through L5, or any one of them, can write to and/orread any transponders positioned at a selected transverse positionacross the web C. While the inductors L1 through L5 write to and/or readan HF RFID transponder T or T′ with or without the shield 82, use of theshield 82 helps limit or confine magnetic energy to the region of thecore or cores 75.

It is noted from FIGS. 5 and 6 that the conductor 38 is at the upstreamside of the inductors L1 through L5. The conductor 38 is effective todiminish the radiation from and to the inductors L1 through L5 fromtransponders T and T′ located upstream of the conductor 38. So while thewriting and/or reading function can be preformed with or without theshield 82 and/or the conductor 38, use of either one is preferred anduse of both the shield 82 and the conductor 38 is most preferred.

With reference to FIG. 10, a connector 84 is used to connect a conductorfrom an RFID reader/writer 85 (FIG. 12) to circuit board 21. Theconnector 84 includes a generally tubular body 86 having four posts 87.An electrically conductive pin 88 extends through the body 86 andprojects through an insulator 89 to a position centrally between theposts 87. The pin 88 includes a connector portion 88′ for connection tothe RFID reader/writer 85. The posts 87 extend through the holes 90 inthe electrically insulating body 21′ of the circuit board 21. The posts87 are soldered at 91 to the conductive area 37. The pin 91 is anchoredto the body 21′ by solder 92 at a non-conductive area 93. The body 86 issoldered to the conductive trace 39 at the area 42.

With reference to FIGS. 11 and 12, the reader/writer 85 is connected viaconductor 94 to the connector portion 88′ of the pin 88. The connectorbody 86 and its pins 87 are grounded. The pin 88 is connected to thetrace 39 which is connected to the resistor R1 which can have aresistance of zero ohm. The capacitors C2 and C3 are connected inparallel to nodes 95 and 96. The capacitor C1 is connected to the node95 and to ground. The windings 79 of the inductors L1 through L5 areconnected in series. The winding 79 of the inductor L1 is connected tothe node 96 and the winding 79 of the inductor L5 is connected toground. The capacitor C2 is a variable capacitor which can be manuallyadjusted. The arrangement of capacitors C1, C2 and C3 is used to tune inthe signal so that the high-frequency magnetic coupler operates at apreferred standard of 13.56 MHz. It is apparent that the coupler 20 canbe made to operate at other frequencies in the high-frequency rangewhich typically is between 3 and 30 MHz. The transponder T receivesforward link commands from the RFID reader/writer 85 using amplitudeshift keying modulation of the 13.56 MHz RF signal. The transponders Tand T′ transmit reverse link data using backscatter modulation.

FIG. 13 is a fragmentary view similar to a portion of FIG. 12, and canbe used when a single inductor L6 is used. The inductor L6 is connectedto the node 96 and to ground. A resistor R2 is connected to the node 96and to ground.

By way of example, not limitation, a typical inductor usable in anembodiment is sold by Coilcraft, located in Cary, Ill., USA under partnumber DS5022P-102ML with an L of 1.0 uH, a DCR (direct currentresistance) max of 0.016 ohms, an SRF (self resonant frequency) type of130, an Insut (saturation current) of 18.0 Amps and an Irms (route meansquare current) of 6.5 Amps. It has overall dimensions of 18.03 and15.24 mm. The longer dimension extends in the longitudinal dimension ofthe web path WP and the shorter dimension extends transverse to the webpath WP. The short dimension of printed circuit board 21 may be 18 mmand may extend in the direction of the web path WP and the longdimension of the printed circuit board may be about 102 mm. Thecenter-to-center spacing of adjacent inductors may be 17 mm. Thesedimensions are not critical, but are preferred in the illustrativeembodiment. The spacing of the inductors is such that transponders T (orT′) can be read at different locations across the web C (or C1) by thecoupler 20.

By way of further example, not limitation, the connector 84 may be theMMCX Straight pc mount jack receptacle type of Johnson Components,Waseca, Minn., USA, sold under part no. 135-3701-201. Any suitableinductors, connectors and components may be used other than the onesdisclosed above.

The cores 75 of the inductors L1 through L5 and L6 are shown to be closeto the transponders T and T′ in web C as is preferred. By way ofexample, not limitation, the distance of the cores 79 to the web C canbe most preferably about 6 mm in the illustrative embodiment.

Typical high-frequency transponders are disclosed in Tag-it HF-ITransponder Inlays Reference Guide, 11-09-21-053, May 2002 of TexasInstruments, Dallas, Tex., USA.

With reference to the embodiment of FIGS. 14 through 19, and initiallyto FIGS. 14 and 15, there is shown a core 100 and a winding 101. Thewinding 101 and the core 100 comprise an inductor 98 of a coupler 99.The core 100 is preferably comprised of ferrite but other magneticablematerials can be used if desired. The core 100 is shown to be elongatein the transverse direction of the longitudinal web W. The core 100preferably extends essentially entirely across the path of the web W sothat there is no gap or zone of weakened magnetic field. The strength ofthe field is essentially constant preferably across the entire width ofthe web W. The winding 101 is shown to surround the core 100. The core100 is shown to have a greater height than the thickness in thedirection of web travel. The winding 101 exists along respectiveupstream and downstream faces 102 and 103 and around terminal ends 105and 106 of the core 100. The winding is shown to have four turns thatlie against faces 102 and 103 and are close to end faces 105 and 106.The core 100 is depicted as adhered to a generally U-shaped parallelconductor 107. The conductor 107 is shown to have wall portions 108 and109 joined to a common wall portion 110. The wall portions 108 and 109are shown to be parallel to each other and to join the wall portion onbase 110 at right angles. The conductor 107 can be comprised of asuitable material such as cooper but other conductive material may beused. The core 100 may be secured to the base 110 by a suitableadhesive. Side or top 111 of the core 100 is spaced inwardly from ends112 which define an opening 112′. The composite web C is spaced slightlyfrom the terminal ends 112 of the walled and their opening 112′.

FIG. 15 shows that connector 86 has five pins 113, 114, 115, 116 and117. Pins 114 through 117 are grounded and anchor the connector 112 tocircuit board 118 and serve as ground connections. The pin 113 isconnected to the RFID reader/writer 85 and to a capacitor C1′. Thecapacitor C1′ connects to the connection 119 made through substrate 126of the printed circuit board 118 and in turn is connected to a tapconductor 120 connected to the top turn 101′ of the winding 101. Theturn 101′ has an end 121 connected by a conductor 122 to one of thegrounded pins 114 through 117. The capacitors C2′ and C3′ connected inparallel are connected by a conductor 123 to end 121′ of the lower turn101″. As is apparent in FIG. 19, the conductor 122 and the capacitorsC2′ and C3′ are connected to ground.

The circuit of FIG. 19 is arranged to match the impedance of the winding101 to the impedance of the RFID reader/writer. The capacitors C2′ andC3′ place the resonant frequency of the cores 100 with the surroundingwinding 101 at a desired operating frequency, for example, an operatingfrequency of 13.56 MHz. At resonance, the impedance of the winding 101is purely resistive (desirable for best match to the reader/writer 85and transmission line connecting the reader/writer 85 to the coupler99), but has an impedance value too high to match the RFID reader/writer85. The capacitor C1′ is optimally used in the circuit connection toprovide DC isolation. By way of example, not limitation, a typicalimpedance of the winding 101 is 4,000 ohms and a typical impedance forthe reader/writer 85 is 50 ohms without considering the remainder of thecircuit.

The bottom face of the printed board has a conductive layer 125 on thenon-conductive substrate 126.

The conductor 107 serves the same purpose as the conductor 38 inlimiting the magnetic radiation that can be radiated beyond theconductive walls 108.

The winding 101 and the core 100 are preferably disposed between andspaced from the walls 108 and 109 and are preferably disposed inwardlyfrom ends 112 of the walls 108 and 109. Thus, the ends 112 of the walls108 and 109 are preferably between the core 100 and the alignedtransponder T. However, depending on the configuration of thetransponder T and the distance between the transponders T along web W,the core 100 can terminate at the same level as the ends 112 of thewalls 108 and 109 or above the ends of the walls 108 and 109.

While the number of turns of the winding 101 is shown to be four, agreater or lesser number can be used. The number of turns of winding 101is mainly a function of the frequency of the signal from and to thereader/writer 85 and the characteristics of the core 100.

Other embodiments and modifications of the invention will suggestthemselves to those skilled in the art, and all such of these as comewithin the spirit of this invention are included within its scope asbest defined by the appended claims.

1. A printer comprising: a print head, a web path for a longitudinallyextending web of record members having longitudinally spaced highfrequency RFID transponders, the web path extending in a downstreamdirection to the print head, and a high frequency magnetic couplerdisposed along the web path, the coupler being capable of magneticallycoupling with the transponders by writing to and/or reading thetransponders one-at-a-time, the coupler including an inductor capable ofradiating and receiving magnetic energy, the inductor having a singlemagnetizable core and an energizable winding coupled to the core, andthe coupler being disposed to radiate or receive magnetic energy at alevel to write to or read a transponder in the web generally alignedwith the core but insufficient to write to or read any transponder inthe web not generally aligned with the inductor, wherein the core iselongate and extends generally transversely across the web path toprovide a substantially uniform magnetic field across the web.
 2. Aprinter as defined in claim 1, the coupler including at least oneconductor upstream of the inductor to diminish magnetic coupling withany transponder upstream of the conductor(s).
 3. A printer as defined inclaim 1, the coupler including at least one conductor downstream of theinductor to diminish magnetic radiation to any transponder down streamof the conductor(s).
 4. A printer as defined in claim 2, the couplerincluding at least one conductor upstream and downstream of the inductorto diminish magnetic coupling to any transponder upstream and downstreamof the conductor(s).
 5. A printer as defined in claim 1, including apair of conductive walls straddling the core.
 6. A printer as defined inclaim 5, where the walls terminate at an opening through which themagnetic radiation can pass, and wherein the core is spaced between thewalls inwardly from the opening.
 7. A printer as defined in claim 1,including a U-shaped conductor having a base and a pair of spaced walls,wherein the walls straddle the core.
 8. A printer as defined in claim 7,where the walls terminate at an opening through which the magneticradiation can pass, and wherein the core is spaced inwardly from theopening.